Methods of forming dislocation enhanced strain in NMOS structures

ABSTRACT

Methods of forming a strained channel device utilizing dislocations disposed in source/drain structures are described. Those methods and structures may include forming a thin silicon germanium material in a source/drain opening of a device comprising silicon, wherein multiple dislocations are formed in the silicon germanium material. A source/drain material may be formed on the thin silicon germanium material, wherein the dislocations induce a tensile strain in a channel region of the device.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a divisional of U.S. patent application Ser.No. 14/912,594, filed Feb. 17, 2016, which is a U.S. National PhaseApplication under 35 U.S.C. § 371 of International Application No.PCT/US2013/061859, filed Sep. 26, 2013, entitled “METHODS OF FORMINGDISLOCATION ENHANCED STRAIN IN NMOS STRUCTURES,” which designates theUnited States of America, the entire disclosure of which are herebyincorporated by reference in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

As microelectronic technology advances for higher performance,integration of high performance transistor devices, such as CMOStransistors devices, becomes increasingly important. CMOS transistorimprovement may involve controlling the strain state of the transistorchannel. Within a CMOS device, an NMOS transistor portion and a PMOStransistor portion may require differing types of channel strainrequirements. For example, the NMOS channel may require a tensile strainin the channel region, while the PMOS channel may require a compressivestrain in the channel region.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming certain embodiments, the advantages of theseembodiments can be more readily ascertained from the followingdescription of the invention when read in conjunction with theaccompanying drawings in which:

FIGS. 1a-1e represent top and cross-sectional views of structuresaccording to various embodiments.

FIG. 2 represents a cross-sectional view of a structure according toembodiments.

FIG. 3 represents a cross-sectional view of a system according toembodiments.

FIG. 4 represents a schematic of a system according to embodiments.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In the following detailed description, reference is made to theaccompanying drawings that show, by way of illustration, specificembodiments in which the methods and structures may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the embodiments. It is to be understood that thevarious embodiments, although different, are not necessarily mutuallyexclusive. For example, a particular feature, structure, orcharacteristic described herein, in connection with one embodiment, maybe implemented within other embodiments without departing from thespirit and scope of the embodiments. In addition, it is to be understoodthat the location or arrangement of individual elements within eachdisclosed embodiment may be modified without departing from the spiritand scope of the embodiments. The following detailed description is,therefore, not to be taken in a limiting sense, and the scope of theembodiments is defined only by the appended claims, appropriatelyinterpreted, along with the full range of equivalents to which theclaims are entitled. In the drawings, like numerals may refer to thesame or similar functionality throughout the several views.

Methods and associated structures of forming and utilizingmicroelectronic structures, such as device structures comprisingstrained source/drain structures, are described. Thosemethods/structures may include forming a thin silicon germanium materialon a source/drain opening of a device comprising silicon, whereinmultiple dislocations are formed in the silicon germanium material, andthen forming a source/drain material on the thin silicon germaniummaterial, wherein the dislocations induce source/drain dislocationsthroughout the source/drain material. The embodiments herein enablestrained channel devices, wherein the source/drain structures may inducea tensile strain in a channel region of the device.

FIGS. 1a-1e illustrate views of embodiments of forming microelectronicstructures, such as NMOS strained silicon transistor structures, forexample. In an embodiment, a device 100 may comprise a substrate portion104 (FIG. 1a , top view). In an embodiment, the substrate 104 maycomprise at least one of a silicon, a non-silicon material, a singlecrystal silicon material, a polysilicon material, a piezoelectricmaterial, III-V material and/or other electromechanical substratematerial. In an embodiment, the device 100 may comprise a portion of aplanar transistor, a multi-gate transistor, such as a tri-gate and/orFinFET transistor, and a nanowire structure.

The device 100 may further comprise a gate structure 102, which maycomprise a portion of a transistor gate structure 102, such as an NMOStransistor gate structure. The device 100 may further comprisesource/drain structures 108. The source/drain structures 108 maycomprise silicon fin structures, in an embodiment, which may beseparated from each other by dielectric material 106. The dielectricmaterial 106 may comprise a STI (silicon trench isolation) material inan embodiment. The dielectric material 106 may provide isolation betweenthe fin structures 108 and the gate electrode 102. In an embodiment, achannel portion of the device 100 may be disposed underneath the gatestructure 102.

In an embodiment, source/drain structures/fins 108 may be removed fromthe substrate portion 104 of the device 100 (FIG. 1b , top view). In anembodiment, an etch process 109 may be employed, such as a wet or dryetch, for example, wherein the silicon of the source/drain/finstructures 108 are removed, leaving an opening 110 in the substrate 104adjacent the STI 106. A channel portion of the silicon underneath thegate electrode remains intact, that is, it remains un-etched by theremoval process/etch process 109. FIG. 1e depicts a cross sectional viewof the device 100, wherein the source/drain fins 108 are removed and theopenings 110 are exposed in a portion of the substrate 104. A channelregion 112 is disposed underneath the gate electrode 102, wherein a gatedielectric layer 114 is disposed between the gate electrode 102 and thechannel region 112. A spacer material 116 may be disposed on the gateelectrode 102.

A dislocation nucleation layer/material 118 may be formed in theopenings 110 (FIG. 1d , cross section). In an embodiment, thedislocation nucleation layer 118 may be selectively grown usingepitaxial growth in the openings 110 on the substrate 104 in thesource/drain regions. In an embodiment, the dislocation nucleation layer118 may comprise a silicon germanium layer 118. The dislocationnucleation layer 118 may be grown such that a plurality of dislocationsmay form in the dislocation nucleation layer 118. In an embodiment, thedislocation nucleation layer 118 may comprise a thickness of about 2 toabout 50 nm.

The dislocation nucleation layer 118 may produce a net strain thatcomprises a tensile strain. In an embodiment, the lattice constant ofthe dislocation nucleation layer 118 may be mismatched (and maycontribute to stress dislocation formation) as compared with thesubstrate 104. In an embodiment, the dislocation nucleation layer 118may comprise a lattice constant that is much larger than the latticeconstant of the substrate 104. For example, the lattice constant maycomprise between 5.43 and 5.66 Å for silicon germanium alloy, and 5.43 Åfor a silicon substrate. In an embodiment, the dislocation nucleationlayer 118 may be formed by epitaxial growth as an initial layer on thesilicon portion of the source/drain openings 110. In an embodiment, thesource/drain openings may comprise NMOS source/drain openings 110.

In an embodiment, when the dislocation nucleation layer 118 comprises asilicon germanium material, the silicon germanium may comprise agermanium concentration of between about ten percent to about eightypercent. In another embodiment, the silicon germanium may be doped withat least one of phosphorus and arsenic. In an embodiment, the phosphorusmay comprise a concentration between about 1016 cm−3 and 1021 cm−3. Inan embodiment, the arsenic may comprise a concentration between about1016 cm−3 and 1021 cm−3. In an embodiment, the dislocation nucleationlayer 118 may comprise a silicon germanium, phosphorus, arsenicconcentration that is substantially evenly distributed throughout thedislocation nucleation layer 118.

In another embodiment, the dislocation nucleation layer 118 may comprisea lower portion comprising a silicon germanium, phosphorus, and arsenicconcentration that is substantially evenly distributed in a lowerportion of the dislocation nucleation layer 118, and may comprise anupper portion comprising substantially a silicon phosphorusconcentration. In another embodiment, the dislocation nucleation layer118 may be grown in the openings 110 as an undoped silicon germaniummaterial that may be subsequently doped by one of an ion implantationand a diffusion doping from a dopant source. In another embodiment, thedislocation nucleation layer 118 may be formed using a molecular beamepitaxial method (MBE), such as a gas source (GS)-MBE method.

In an embodiment, a rapid thermal chemical vapor deposition (RT-CVD)reactor or a CVD reactor may be used to grow the dislocation nucleationlayer 118. In an embodiment, a process to grow the dislocationnucleation layer 118 may include the use of silane, germane, digermane,phosphine, and hydrochloric acid with a hydrogen carrier gas. Atemperature of 700 degrees Celsius and a pressure of 20 Torr may beemployed. The parameters for the dislocation nucleation layer 118 growthprocess may vary depending upon the particular application. In anembodiment, the growth parameters may be optimized for the formation ofa plurality of defects. In an embodiment, a large number ofdislocations/defects 120 may be formed/initiated at the interfacebetween the substrate 104 and the dislocation nucleation layer 118.

In an embodiment, a source/drain material 122 may be selectively formedon the dislocation nucleation layer 118 after sufficient defect 120formation in the dislocation nucleation layer 118 (FIG. 1e , crosssection). In an embodiment, the source/drain material 122 may compriseof silicon or silicon carbon alloy material. In an embodiment, thesource/drain material 122 may comprise a thickness of about 5 to about100 nm. In an embodiment, the dislocation nucleation layer 118 mayprovide a source of dislocations/defects 120 that may inducesource/drain dislocations 124 in the source/drain material/structure122. In an embodiment, the dislocation nucleation layer 118 and thesource/drain material 122 may comprise a source/drain fin structure 123.

In an embodiment, the dislocations 124 in the source/drain material 122may continue to propagate up towards a free surface 125 of thesource/drain material 122. In an embodiment, the multiple dislocations124 disposed in the source/drain material 122 may cause a flipping ofthe strain imparted by the lattice mismatched dislocation nucleationlayer 118 from a compressive to a tensile strain in the channel region112. In an embodiment, overlapping strain fields from each dislocation124 can overcome the compressive stress that may be present in thedislocation nucleation layer 118, such as a silicon germanium layer 118.In an embodiment, the source/drain material 122 may impart a tensilestrain on the channel region 112 along a conduction direction for thedevice 100, which may comprise a transistor device in embodiments.

In an embodiment, the device 100 may comprise circuitry elements such astransistor structures including planar, trigate and nanowire transistorstructures, and any other suitable circuitry elements. The circuitryelements may comprise logic circuitry for use in a processor die, forexample. Metallization layers and insulative material may be included inthe device 100, as well as conductive contacts/bumps that may couplemetal layers/interconnects to external devices. transistor device. Thetype of elements included in the device 100 may comprise any suitabletype of circuit elements, according to the particular application.

FIG. 2 depicts a cross-sectional views of an embodiment comprising adevice structure 200, wherein the device comprises a nanowire In anembodiment, the device 200, such as a nanowire device 200, may comprisea substrate 204 disposed below a channel region 212. A dislocationnucleation layer 218 may comprise a plurality of defects/dislocations220. A source/drain material 222 may comprise a plurality ofdefects/dislocations 224. A gate electrode 202 may be disposed on a gatedielectric 214. A nanowire material 203, such as silicon, may bedisposed underneath the gate dielectric 214. A wrap around gatedielectric 205 may be disposed beneath the wrap around nanowire material203. A wrap around gate electrode 207, may be disposed underneath thewrap around gate dielectric 205. The channel region comprises an inducedstrain from the dislocations from the source/drain material 222.

In an embodiment, the device 100 of the embodiments may be coupled withany suitable type of package structures capable of providing electricalcommunications between a microelectronic device, such as a die and anext-level component to which the package structures may be coupled(e.g., a circuit board). In another embodiment, the device may becoupled with a package structure that may comprise any suitable type ofpackage structures capable of providing electrical communication betweena die and an upper integrated circuit (IC) package coupled with thedevice layer.

The device described in the various Figures herein may comprise aportion of a silicon logic die or a memory die, for example, or any typeof suitable microelectronic device/die. In some embodiments the deviceof the embodiments may further comprise a plurality of dies, which maybe stacked upon one another, depending upon the particular embodiment.In some cases the device may be located/attached/embedded on either thefront side, back side or on/in some combination of the front and backsides of a package structure. In an embodiment, the device may bepartially or fully embedded in a package structure.

The various embodiments of the strained channel devices herein enablestrain transfer from the source/drain region of an NMOS source/drainregion to an NMOS channel region. The strain transfer is accomplishedthrough the use of dislocation strain fields in the NMOS source/drainregions. Some prior art methods of achieving channel strain haveinvolved employing buffer layers of mismatched lattice constantmaterials under the channel region, and employing dopants in thesource/drain region. The embodiments herein include employing adislocation nucleation layer, such as silicon germanium, to propagateoverlapping strain fields that induce tensile strain in the channelregion. Since the growth takes place only within the source/drainregion, the embodiments, avoid performance degradation into the channelas seen when utilizing buffer layers, as in the prior art.

Turning now to FIG. 3, illustrated is an embodiment of a computingsystem 300. The system 300 includes a number of components disposed on amainboard 310 or other circuit board. Mainboard 310 includes a firstside 312 and an opposing second side 314, and various components may bedisposed on either one or both of the first and second sides 312, 314.In the illustrated embodiment, the computing system 300 includes apackage structure 340 disposed on the mainboard's first side 312,wherein the package structure 340 may comprise any of the devicestructures, such as the transistor device structures of the embodimentsdescribed herein.

System 300 may comprise any type of computing system, such as, forexample, a hand-held or mobile computing device (e.g., a cell phone, asmart phone, a mobile internet device, a music player, a tabletcomputer, a laptop computer, a nettop computer, etc.). However, thedisclosed embodiments are not limited to hand-held and other mobilecomputing devices and these embodiments may find application in othertypes of computing systems, such as desk-top computers and servers.

Mainboard 310 may comprise any suitable type of circuit board or othersubstrate capable of providing electrical communication between one ormore of the various components disposed on the board. In one embodiment,for example, the mainboard 310 comprises a printed circuit board (PCB)comprising multiple metal layers separated from one another by a layerof dielectric material and interconnected by electrically conductivevias. Any one or more of the metal layers may be formed in a desiredcircuit pattern to route—perhaps in conjunction with other metallayers—electrical signals between the components coupled with the board310. However, it should be understood that the disclosed embodiments arenot limited to the above-described PCB and, further, that mainboard 310may comprise any other suitable substrate.

In addition to the package structure 340, one or more additionalcomponents may be disposed on either one or both sides 312, 314 of themainboard 310. By way of example, as shown in the figures, components301 a may be disposed on the first side 312 of the mainboard 310, andcomponents 301 b may be disposed on the mainboard's opposing side 314.Additional components that may be disposed on the mainboard 310 includeother IC devices (e.g., processing devices, memory devices, signalprocessing devices, wireless communication devices, graphics controllersand/or drivers, audio processors and/or controllers, etc.), powerdelivery components (e.g., a voltage regulator and/or other powermanagement devices, a power supply such as a battery, and/or passivedevices such as a capacitor), and one or more user interface devices(e.g., an audio input device, an audio output device, a keypad or otherdata entry device such as a touch screen display, and/or a graphicsdisplay, etc.), as well as any combination of these and/or otherdevices.

In one embodiment, the computing system 300 includes a radiation shield.In a further embodiment, the computing system 300 includes a coolingsolution. In yet another embodiment, the computing system 300 includesan antenna. In yet a further embodiment, the assembly 300 may bedisposed within a housing or case. Where the mainboard 310 is disposedwithin a housing, some of the components of computer system 300—e.g., auser interface device, such as a display or keypad, and/or a powersupply, such as a battery—may be electrically coupled with the mainboard310 (and/or a component disposed on this board) but may be mechanicallycoupled with the housing.

FIG. 4 is a schematic of a computer system 400 according to anembodiment. The computer system 400 (also referred to as the electronicsystem 400) as depicted can embody/include a package structure thatincludes any of the several disclosed device embodiments and theirequivalents as set forth in this disclosure. The computer system 400 maybe a mobile device such as a netbook computer. The computer system 400may be a mobile device such as a wireless smart phone. The computersystem 400 may be a desktop computer. The computer system 400 may be ahand-held reader. The computer system 400 may be integral to anautomobile. The computer system 400 may be integral to a television.

In an embodiment, the electronic system 400 is a computer system thatincludes a system bus 420 to electrically couple the various componentsof the electronic system 400. The system bus 420 is a single bus or anycombination of busses according to various embodiments. The electronicsystem 400 includes a voltage source 430 that provides power to theintegrated circuit 410. In some embodiments, the voltage source 430supplies current to the integrated circuit 410 through the system bus420.

The integrated circuit 410 is electrically, communicatively coupled tothe system bus 420 and includes any circuit, or combination of circuitsaccording to an embodiment, including the package/device structures ofthe various embodiments included herein. In an embodiment, theintegrated circuit 410 includes a processor 412 that can include anytype of packaging structures including vertical passive structuresaccording to the embodiments herein. As used herein, the processor 412may mean any type of circuit such as, but not limited to, amicroprocessor, a microcontroller, a graphics processor, a digitalsignal processor, or another processor. In an embodiment, the processor412 includes any of the embodiments of the package structures disclosedherein. In an embodiment, SRAM embodiments are found in memory caches ofthe processor.

Other types of circuits that can be included in the integrated circuit410 are a custom circuit or an application-specific integrated circuit(ASIC), such as a communications circuit 414 for use in wireless devicessuch as cellular telephones, smart phones, pagers, portable computers,two-way radios, and similar electronic systems. In an embodiment, theprocessor 412 includes on-die memory 416 such as static random-accessmemory (SRAM). In an embodiment, the processor 412 includes embeddedon-die memory 416 such as embedded dynamic random-access memory (eDRAM).

In an embodiment, the integrated circuit 410 is complemented with asubsequent integrated circuit 411. In an embodiment, the dual integratedcircuit 411 includes embedded on-die memory 417 such as eDRAM. The dualintegrated circuit 411 includes an RFIC dual processor 413 and a dualcommunications circuit 415 and dual on-die memory 417 such as SRAM. Thedual communications circuit 415 may be configured for RF processing.

At least one passive device 480 is coupled to the subsequent integratedcircuit 411. In an embodiment, the electronic system 400 also includesan external memory 440 that in turn may include one or more memoryelements suitable to the particular application, such as a main memory442 in the form of RAM, one or more hard drives 444, and/or one or moredrives that handle removable media 446, such as diskettes, compact disks(CDs), digital variable disks (DVDs), flash memory drives, and otherremovable media known in the art. The external memory 440 may also beembedded memory 448. In an embodiment, the electronic system 400 alsoincludes a display device 450, and an audio output 460. In anembodiment, the electronic system 400 includes an input device such as acontroller 470 that may be a keyboard, mouse, touch pad, keypad,trackball, game controller, microphone, voice-recognition device, or anyother input device that inputs information into the electronic system400. In an embodiment, an input device 470 includes a camera. In anembodiment, an input device 470 includes a digital sound recorder. In anembodiment, an input device 470 includes a camera and a digital soundrecorder.

Although the foregoing description has specified certain steps andmaterials that may be used in the methods of the embodiments, thoseskilled in the art will appreciate that many modifications andsubstitutions may be made. Accordingly, it is intended that all suchmodifications, alterations, substitutions and additions be considered tofall within the spirit and scope of the embodiments as defined by theappended claims. In addition, the Figures provided herein illustrateonly portions of exemplary microelectronic devices and associatedpackage structures that pertain to the practice of the embodiments. Thusthe embodiments are not limited to the structures described herein.

What is claimed is:
 1. A semiconductor structure, comprising: a siliconbody extending from a single crystalline silicon substrate through anisolation region, the isolation region having a top surface, and thesilicon body having a top and laterally opposite sidewalls, wherein thetop of the silicon body is above the top surface of the isolationregion; a gate electrode over the top of the silicon body and adjacentto the laterally opposite sidewalls of the silicon body, the gateelectrode over a portion of the isolation region, and the gate electrodedefining a channel region in the silicon body; a first silicon germaniumdislocation nucleation layer in a first recess in the silicon bodylaterally adjacent a first end of the channel region at a first side ofthe gate electrode; a silicon source region on the first silicongermanium dislocation nucleation layer, the silicon source regioncomprising a first plurality of dislocations; a second silicon germaniumdislocation nucleation layer in a second recess in the silicon bodylaterally adjacent a second end of the channel region at a second sideof the gate electrode, the second side of the gate electrode oppositethe first side of the gate electrode; a silicon drain region on thesecond silicon germanium dislocation nucleation layer, the silicon drainregion comprising a second plurality of dislocations, wherein a top ofthe silicon drain region is spaced apart from a top of the siliconsource region by a first distance, and a bottom of the silicon drainregion is spaced apart from a bottom of the silicon source region by asecond distance greater than the first distance; a first dielectricspacer adjacent the first side of the gate electrode; and a seconddielectric spacer adjacent the second side of the gate electrode.
 2. Thesemiconductor structure of claim 1, further comprising: a gatedielectric between the gate electrode and the channel region of thesilicon body.
 3. The semiconductor structure of claim 1, wherein thefirst plurality of dislocations of the silicon source region and thesecond plurality of dislocations of the silicon drain region provide astrain to the channel region in the silicon body.
 4. The semiconductorstructure of claim 3, wherein the strain is a tensile strain.
 5. Thesemiconductor structure of claim 1, wherein the silicon body is asilicon fin.
 6. The semiconductor structure of claim 1, wherein thesilicon source region and the silicon drain region are doped with N-typedopants selected from the group consisting of phosphorous and arsenic.7. A system, comprising: a circuit board; and a package structurecoupled to the circuit board, the package structure comprising a diecoupled to a package, the die comprising: a silicon body extending froma single crystalline silicon substrate through an isolation region, theisolation region having a top surface, and the silicon body having a topand laterally opposite sidewalls, wherein the top of the silicon body isabove the top surface of the isolation region; a gate electrode over thetop of the silicon body and adjacent to the laterally opposite sidewallsof the silicon body, the gate electrode over a portion of the isolationregion, and the gate electrode defining a channel region in the siliconbody; a first silicon germanium dislocation nucleation layer in a firstrecess in the silicon body laterally adjacent a first end of the channelregion at a first side of the gate electrode; a silicon source region onthe first silicon germanium dislocation nucleation layer, the siliconsource region comprising a first plurality of dislocations; a secondsilicon germanium dislocation nucleation layer in a second recess in thesilicon body laterally adjacent a second end of the channel region at asecond side of the gate electrode, the second side of the gate electrodeopposite the first side of the gate electrode; a silicon drain region onthe second silicon germanium dislocation nucleation layer, the silicondrain region comprising a second plurality of dislocations, wherein atop of the silicon drain region is spaced apart from a top of thesilicon source region by a first distance, and a bottom of the silicondrain region is spaced apart from a bottom of the silicon source regionby a second distance greater than the first distance; a first dielectricspacer adjacent the first side of the gate electrode; and a seconddielectric spacer adjacent the second side of the gate electrode.
 8. Thesystem of claim 7, wherein the die is a die selected from the groupconsisting of a logic die and a memory die.
 9. The system of claim 7,further comprising: an additional component coupled to the circuitboard, the additional component selected from the group consisting of abattery and a wireless communication device.
 10. The system of claim 7,further comprising: one or more user input devices coupled to thecircuit board.